-2-w is equivalent to -24 - 12w all you have to do is simplify the expression!
A=adult
c=children
total lumber=30
total number=adults+children
a+c=30
total cost=50
total cost=acost+ccost
acost=a times cost per adult=a times 3=3a
ccost=c times cost per child=c tiems 1=1c=c
total cost=3a+c
50=3a+c
equiaotn are
a+c=30
3a+c=50
multiplyu first by -1 and add
3a-a+c-c=50-30
2a=20
a=10
sub
10+c=30
c=20
answer is A
